X-Mozilla-Keys:
I would imagine that "recycling" the portion of the charge that didn't
burn the first time around will really pay off, but I don't think that
it will ever compete with modern piston engines. The Honda VTEC engine
has a BSFC of about .43 tuned for best power. The Mazda V6 that we
messed with was pretty close to that, but I don't remember the exact
number. Maybe .45 or .46. Very impressive!
PY
By agressive leaning at altitude Tracy is seeing 0.47 or 0.48 with the
rotary which is not that far away from a Mazda V6 piston engine.
It is very interesting to see those numbers Paul. Almost everybody
advocating water cooled car piston engines assumes BSFC is well below
0.40. Actually water cooling is a drawback as running an engine
at 212 F means more heat energy is given up to the coolant while
an aircooled aircraft engine will run 300 degrees or above.
The Continental SAE paper mentioned on the ACRE NL web site
http://home.earthlink.net/~rotaryeng/ on liquid cooled aircraft
engines discusses this factor at length. Continental was
able to get the liquid cooled Voyager aircraft engine
series below 0.40.
BTW the number I have for the big block Chevy is 0.53.
Paul Lamar
Z wrote:
Not to say that I disagree, but I think that is definitely an open question. There are
two pieces to the overall efficiency equation, first, combustion efficiency, (efficiency
of converting chemical potential energy to heat), second, thermodynamic efficiency
(efficiency of converting heat energy to mechanical work).
There is no question that rotary engines will never equal reciprocating engines in
the realm of combustion efficiency, for the reasons others have already stated.
However, it is important to remember that the thermodynamic efficiency of the rotary
engine cycle is considerably better than that of the piston engine cycle. This was one
of the things which helped spur interest in the rotary engine in the first place. With
properly timed intake and exhaust (allowing full extraction of the available heat energy
during the expansion phase), the greater thermodynamic efficiency of the conventional
rotary cycle is more than capable of offsetting the lower combustion efficiency.
If you go beyond this and start talking about using the intake air itself to cool
the rotors and rotor housings, the achievable overall efficiency of the rotary
configuration in fact considerably exceeds that which can be realized in a piston
engine, a fact which the Moeller rotary has already demonstrated.
BTW about the "Z".
This was sent from Cornell Education and the email address is not on our
list. I have no idea who this is. I wish I did because he sounds like he
has a lot to offer.
Paul Lamar
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